The persons skilled in the art about the structure of color mixing LED and the method of making the same ever submitted several relevant documents. For example, Nichia Chemical Industries, Ltd. submitted that the fluorescent powder could be utilized (U.S. Pat. Nos. 5,998,925/6,069,440), wherein the blue light LED can be used to excite yttrium-aluminum-garnet (YAG) fluorescent body to generate yellow light that can be mixed with the original blue light into white light. In this method, the YAG fluorescent material is coated on the InGaN blue light chip having a wavelength of 460 nm; then the blue light LED is used to illuminate the fluorescent material to generate yellow light that has a wavelength of 555 nm and is complementary to blue light; and then the principle of lens is applied to mix the complementary yellow light and blue light to obtain the output of white light. Even though this method has the advantage of low cost, yet the light-emitting efficiency is worse (due to the low opto transformation efficiency of YAG fluorescent material), so that the output of high power cannot be obtained. Moreover, the temperature and the operating current easily cause the change of wavelength of blue light LED, hence the light-emitting efficiency of YAG becomes worse (the opto transformation efficiency of YAG fluorescent material changes as the wavelength of blue light LED changes); and it is very difficult to achieve output of white light having high output intensity and under steady operation.
Besides, ORSAM Opto Semiconductors submitted that three LEDs emitting three basic colors—red, green, and blue of light respectively could be packaged together to generate white light. In such a method, it is necessary to adjust the wavelength and brightness of the three LEDs respectively in order to obtain purer white color; hence the light-emitting color cannot be controlled easily. Moreover, perhaps the colors will be mixed non-uniformly due to the three independent light sources. Furthermore, since the semiconductor materials of the LEDs emitting three basic colors—red, green, and blue of light respectively are quite different from each other, therefore the design of the driving circuit becomes rather complicated and hence the manufacturing cost is higher.